Due to the world-wide increasing focus on energy consumption, more and more attention is paid to lamps commonly referred to as “energy saving” lamps, such as Compact Fluorescent Lamps (CFL), which are energy efficient by consuming up to five times less energy than the conventional incandescent lamps.
However, due to the electrical nature of both the phase-cut dimmers and the CFL circuits, they do not work together as well as the incandescent lamps and dimmers. Moreover, some people do not have phase-cut dimmers installed. Although installing a phase-cut dimmer is not very complicated, many people hesitate to install one because of the dangerously high mains voltage.
The solution would be to have a lamp that is always dimmable by selecting either phase-cut dimming or step dimming, knowing that an end user will be able to step dim with a phase-cut dimmer, although not logical.
At this respect, EP08103192.4 discloses a waveform detection circuit for a CFL controller adapted to detect a rectified phase-cut or sinusoidal waveform using its duty cycle and in response, to select the respective dim mode amongst the linear phase-cut dimming and the step dimming, the latter being defined by several fixed values at a mains voltage independent level. The duty cycle is determined based on the fact that the phase-cut dimmers always cut off at least some part of the sinusoid of the mains voltage, as it is illustrated in FIG. 1 depicting conventional AC mains supplied waveforms without (A-sinusoidal waveform) and with phase-cut dimming (B-forward phase-cut waveform and C-reverse phase-cut waveform). However, it may turn out that phase-cut dimmers connected to CFL driver circuits do not produce such perfect waveforms, and in particular that the cut-off part does not drop to zero very fast. Thus, in addition to the phase detection circuitry, supplemental circuitry might be needed to create the required cut-off curves, thereby rendering the circuitry quite complex.